Lapping apparatus



-March 26, 1940. D. A. WALLACE LAPPING APPARATUS Original Filed Jan. 30, 1937 Patentedv Mar. 26, 1940 UNITED STATES,

LAPPING APPARATUS David A. Wallace, Detroit, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a

corporation of Delaware Original application January 30, 1937, Serial No. 123,119. Divided and this application April 27, 1938, Serial No. 204,572

3 Claims.

This invention relates to an improved apparatus for lapping the surfaces of cylindrical bores and for accurately bringing the latter to true cylindrical contour and is a division of my application, Serial No. 123,119, filed January 30, 1937.

One of the main objects of the invention is to provide an improved expansible lap for lapping cylindrical surfaces.

Other objects of the invention are to provide a device of thisV character which has a plurality of lapping elements arranged in spaced series and which is adapted to operate simultaneously upon the walls of a plurality of aligned bores in order to accurately bring such Walls into concentric relationship with respect to a common axis; to provide means for adjustably supporting a plurality of lapping elements in arcuately arranged relationship so that they may expand and contract in order to accommodate the lap to the finishing of bores of diierent diameters; to provide means of this kind by which the lapping elements are yieldably urged outwardly toward an adjustably selected predetermined limiting position in order to accommodate operation of the lap in an underside bore and to facilitate lapping thereof to a predetermined diameter; and to provide means in a multiple lap of thischaracter for accurately holding the adjustable lapping elements thereof in alignment with their axisv of rotation so that the lap will form the Walls of the bore to a true cylindrical contour and the positions of the lapping elements will not be determined by the rough contour of the walls of the bore.

Other objects of the invention are to provide a lap of this kind that has an outer tubular casing Which sustains the main portion of the strains and stresses to Which the device is subjected in operation and which is provided With an inner surface of comparatively large area that serves as a reference surface for predetermining the positions of the lapping elements and maintaining the same in accurate parallelism with the axis of the tool; and to provide a lapping element adjustment control member in a device of this kind which is relieved of all lapping element supporting functions.

An illustrative embodiment of the invention is shown in the accompanying drawing, in which:`

Fig. lis a plan View of a lapping tool embodying f the invention.

Fig. 2 is an enlarged, fragmentary, central, lonof Fig. 1.

Fig. 3 is an end elevational view taken from the right as viewed in Fig. 1.

Fig. 4 is a transverse sectional View taken on the line44 of`Fig. 2.

Fig. 5 is -a transverse sectional View taken on 5 the line 5 5 of Fig. 2.

In the form' of the invention illustrated in the drawing, the multiple expansible lapping tool, generally designated by the numeral 1|, and illustrated inI Figs. 1 to 5, inclusive, `comprises a tubular casing 91 having a plurality of axially spaced series of circumferentially arranged slots 98 which extend axially of the casing. Radially slidably mounted in each slot 98 is a lapping member comprising a lapping element, preferably 15 including either natural or compressed stone 99 and a lapping element carrier |00 having a groove in its outer side in which its lapping element is securely mounted. The lapping elements may comprise either natural or'artificial stone or any suitably lapping abrasive, or polishing material. The lapping element carriers |00 taper in width and their extremities are slidably engaged with the extremities of the slots 98 in order to guide the movement of the lapping members. Each lapping element carrier |00 has a substantially axially extending outer surface |0| and an inner surface |02 which is inclined with respect to the longitudinal axis of the tubular casing 91, as viewed in Fig. 2. The lapping members are yieldably urged inwardly toward the centerof the tubular casing 91 by springs |03 which are secured by screws |04 to the casing 91 and which have free end portions resiliently engaging the outer surface |0| of each lapping element carrier |00, respectively.

Slidably mounted on the interior of the tubular casing 91, and associated with each series of lapping element carriers |00 is a spreader member, generally designated by the numeral |05, which is adapted to uniformly urge all lapping elements of each series outwardly against the action of the springs |03. The spreader elements |05 are of generally cylindrical shape and they are provided with longitudinally extending slots |06 which are inclined with respect to its longitudinal axis for receiving the lapping element carriers |00. The bottom walls |01 of the slots |06 are inclined relative to the axis of the tubular casing 91 as to be parallel to the inclination of the inner surfaces |02 of the lapping element carriers |00. Formed in the periphery of the spreader member |05 are a plurality of arcuately spaced, substantially semicylindrical grooves |08 which are provided to reduce the the inner cylindrical surface of the tubular casing 91 Between the grooves |08 are ribs |09 which have outer extremities conforming in curvature to the cylindrical contour of the inner periphery of the casing 91. These rib extremities therefore provide substantial surface contact between'the inner cylindrical surface of the casing 91 and the spreader element |05 throughout substantially the entire length of the latter so as to accurately pilot the spreader member within the 'casing 91 and to prevent relative radial movealnt of the spreader with respect to the casing. By virtue of this construction the outer working surfaces of the lapping elements 99 are accurately held in parallel relationship with respect to the axis of the casing 91, while the lapping elements are disposed in their various differently spaced relationships from the axis of the casing.

Apparatus for adjustably positioningv the lapping elements 99 radialy of the casing 91 is illustrated in Figs. l to 5, inclusive. This apparatus comprises an adjusting bar disposed centrally of the interior of the`casing 91 and extending substantially throughout the entire length thereof so as to simultaneously operate upon the spreader member |05 of each of the longitudinally spaced series of lapping elements respectively. The left end of the rod as viewed in Fig. 2, is non-rotatably secured to a cross head member H2 slidably mounted within the casing 91 by a pin H3', The cross head member ||2 is provided with a diametrically extending passage ||3 in' which a pin llt is disposed. The pin |||l has reduced end portions ||5 which extend outwardly beyond the exterior surface of the casing 91 through axial slots H6 formed therein. The pin ||ll has its end portions slidably engaged in helical slots ||6 formed in a collar ||1 surounding the casing 91. Rotative movement of the collar l1 relative to the casing 91 while the collar is held against axial movement in the casing, as hereinafter set forth, causes the rod and cross head ||2 to be shifted axially of the casing 91 by reason of the camming action provided between the outer periphcry of the end portions of the pin H4@ and the side walls o f the slots H5.

Provided on the exterior of. the left end portion of the casing 91 is apparatus for releasably holding the collar ||1 against movement axially of the casing 91 while accommodating yrotative movement thereof relative to the casing. The collar H1, pin lill and cross head H2 as well as the bar are moved in unison axially of the bar. The collar ||1 is concentrically mounted on the outer periphery of the casing 91 and its helical slots ||6 receive bushings ||8 in which the reduced end portions ||5 of the pin ||4 are received. The bushings I8 are held in assembled relationship on the reduced'end portions H5 byscrews H9 threaded in apertures formed in opposite extremities of the pin Il. Non-rotatably mounted on the collar ||1 is a sleeve |20 which is secured to the collar ||1 by rivets |2|. The sleeve |20 has an inwardly extending radial flange |22 on its right extremity, as viewed in Fig. 2, which is spaced axially from the right extremity of the collar |1. Threaded on the left end portion of the casing 91 is a collar |23 having an outwardly extending radial ange |24 disposed between the inwardly extending iiange |22 of the sleeve 20 and the right extremity of the collar ||1, as viewed in Fig. 2. Interposed `between the surface area contact between the spreader andextremities of the collar ||1 and the collar |23 is a thrust bearing member |25. The collar |23 is provided with recesses |26 for receiving lugs of a spanner wrench by which the threaded collar |23 may be turnedv relative to the casing 91 in order to shift the collar ||1 and the pin ||4 as well as the cross heads ||2 and the rod in either direction axially of the casing. A locking ring |21 is also threaded on the left end portion of the casing 91 and located adjacent the right extremity of the collar |23 for the purpose of securely xing the collar |23 against unintended rotation relative to the casing. When the locking ring |21 is released, the threaded collar |23 may be turned in either direction to shift the adjustment bar axially in respectively corresponding directions. This adjustment varies the limit of expansion and contraction of the lapping stones which may be produced by rotation of the collar |1 relative to the casing 91.

A stop |28 is fixed on the adjusting bar adjacent the right extremity of each spreader element |05 and is secured to the bar by a pin |29. A stop |30 is mounted on the adjusting bar |||`in spaced relation to the right end of each spreader element |05, as viewed in Fig. 2, and secured to the bar by a pin 3| Interposed between the right extremity of. each spreader element |05 and the associated stop |30, respectively, is a coil spring |32 by which the spreader elements are yieldably urged leftwardly, as Viewed in Fig 2, toward the stops |28. In this manner, tue lapping elements of all of the longitudinally spaced series thereof are yieldably urged outwardly by the inclined surfaces |01 of the spreader element |05. The limiting outward positions yto which the lapping elements 99 may be moved by the spreader elements |05 may be selectively predetermined by adjustably positioning the stops |23 and |30 by releasing the locking ring |21 and moving the collar ||1 and rod ||l axially in the foregoing manner. Thus, when the lapping tool is inserted in an undersized bore, the lapping elements may be contracted by turning the collar ||1 relative to the casing 91 so as to become accommodated to the bore and during the lapping operation the lapping elements are gradually moved outwardly as the diameter of the bore is increased to accommodate such outward movement until the left ends of the spreader elements |05 engage their respective stops |29 which prevent further outward'movement of the lapping elements and thereby facilitate accurate predetermining of the diameter of the cylindrical bore operated upon. The collar may be rotatively adjusted during operation functionally retarding or increasing rotation of the collar as the tool is rotating.

A Vlapping tool of the foregoing character may operate simultaneously upon a plurality of spaced bores such as are presented .by the main bearings of a multiple cylinder internal combustion engine cylinder block, or-if desired the lapping tool may comprise only one series of arculately arranged lapping elements of any desired length which may be employed to lap a single cylinder bore'such as the cylinder bore of a cylinder block. Internal cylindrical surfaces formed to true cylindrical contour while the working surfaces of the stones are accurately held in cylindricalarrangements and they are vof the tool in any suitable manner such as by are accurately rigidly held against vibratory or other displace- In order to facilitate convenient coupling of the lapping tool to an operating shaft of a lapping machine, there is provided at the left extremity of the tool a universaltype of coupling mechanism comprising a connecting shaft |33 having a ball |34 on its right end, as viewed in Fig. 2, which is disposed within the left end portion of the casing 91 and swivelled in a cylindrical block |35 which is splined in the interior of the casing. The block |35 has a diametrically extending passage |36 in which the end portions of a pin |37 extending through the ball v|311 are disposed. The block |35 is held against outward displacement from the casing 91 by a threaded collar |38. Provided on the louter extremity of the shaft |33 is a knob |39 having a pin |4 extending therethrough by which the shaft |33 may be conveniently detachably connected with the nal driving shaft or member of a, lapping machine.

Although but one specific embodiment of the invention is herein shown and described, it will be understood thatvarious changes in the size, shape and arrangement of parts may be made without departing from the spirit of my invention.

What I claim is:

l. An expansible lap comprising a tubular casing having a plurality of circumferentially spaced openings therein, a lapping element carrier s-lidably mounted in each opening respectively and movable toward and away from the longitudinal axis of said casing, each of said lapping element carriers having an inner surface inclined with respect to said axis, a lapping element on the outer side of each carrier, means for adjustably positioning said lapping elements at divers distance from said axis including a cam member having a passage therethrough shiftably axially of said casing and having end portions guided by the internal surfaces thereof located at opposite extremities of said openings and having taber having an abutment located beyond one extremity of the latter, resilient means bearing between said abutment and the adjacent end of said cam member for urging lsaid member axially of said casing toward a position corresponding to the maximum outward positions of said lapping elements, a stop on said control bar located beyond the opposite end of said cam member for positively limiting movement of said member by said resilient means, and an adjustable member on said casing operatively connected with said bar for selectively positioning said stop and abutment at -diverse locations. y

2. A. multiple expansible lap comprising a cylindrical tube having axially spaced series of circumferentially arranged slots therein, a lapping member shiftably mounted in each slot and movable toward and away from the longitudinal axis of said tube, lapping element spreaders axially shiftably mounted in said tube, one associated with the lapping members of each of said series of slots respectively, an adjustable control member axiallyshiftably mounted in said tube and movable axially relative to said spreaders, stops on said control member for selectively positively limiting movement of said spreaders toward positions corresponding to maximum outward positions of said lapping members, and a spring axially relative to said spreaders, stops on said control member for limiting movement of said spreaders in the direction of movement thereof which causes expansion of said lapping members, a spring bearing between said control member and each spreader respectively for normally urging the latter toward its associated stop, and means coacting between said hollow tube and said control member for releasably holding the latter in a selected position.

DAVID A. WALLACE. 

